Gut bacteria have been linked to autoimmune diseases such as lupus which don't primarily impact the gastrointestinal system. However their influence on the human immune system remains poorly understood.

In a recent study Yale researchers revealed that the gut bacterium Enterococcus gallinarum can migrate beyond the gastrointestinal tract and trigger an autoimmune response. These findings may pave the way for new diagnostic and treatment strategies for autoimmune conditions.

The human body harbors a diverse range of bacteria collectively known as the microbiome which play a crucial role in maintaining health. However certain native bacteria can become harmful under specific conditions these are referred to as pathobionts.

E. gallinarum a pathobiont present in the microbiome has been shown to promote lupus in mouse models and has been found in tissues beyond the gut in patients with the disease.

In their new study Yale researchers Noah Palm professor of immunobiology at Yale School of Medicine (YSM) and Martin Kriegel an adjunct associate professor at YSM sought to uncover how E. gallinarum exerts its immune effects. Palm and Kriegel served as co-senior authors of the study.

Using both human cellular models and mouse studies the researchers discovered that after leaving its primary habitat in the gut E. gallinarum travels to the lymph nodes and liver before eventually reaching the spleen. The lymph nodes and spleen are secondary lymphoid organs integral to the immune system's ability to mount immune responses. The team suggests that these organs are where the bacterium initiates its widespread autoimmune effects.

T cells are a type of white blood cell that can develop into inflammatory T helper 17 (Th17) cells. The study revealed that E. gallinarum prompts the transformation of Th17 cells in the spleen and blood. These cells then stimulate the maturation of other immune cells which subsequently produce autoantibodies antibodies that mistakenly target the body's own tissues instead of pathogens.

One challenge with autoimmune diseases is that we don’t fully understand how they originate explained Kriegel who is also a professor at the University of Münster in Germany. These findings help us piece together the puzzle offering insights into potential triggers and drivers of these conditions.In the future treatments for autoimmune diseases might not focus solely on the immune system said Kriegel. We could also target the bacteria that trigger these conditions.

Source: https://news.yale.edu/2025/02/05/study-reveals-how-gut-bacteria-might-trigger-autoimmune-diseases-lupus